Lapping device



Feb. 2, 1965 c. D. HARRISON 3,167,886

LAPPING DEVICE Filed Dec. 22, 1961 '2 sheets-sheet 1 Uilm I @Unmlk- 1 1 I I l t] 15 i l C ze I 1 .l 3 l l/ am. y "I i? l;

IN VEN TOR. CHARLES D HARP/50H ATTORNEY Trae/ver C. D. HARRISON LAPPING DEVICE Feb. 2, 1965 Filed Dec. 22, 1961 2 Sheets-Sheet v2 Y www@ M70 mummm Na/W 1S m m C BYQ.n

United States Patent O M 3,167,836 LAPPiNG DEVICE Charles D. Harrison, Fort Worth, Tex., assigner to General Dynamics Corporation, San Diego, Cali, a corporation of Delaware Filed Dec. 22, 196i, Ser. No. 161,527 ,Claims. (Cl. Sli-2o) The present invention relates generally to lapping devices, and more particularly to a device adapted for lapping objects having spherical surfaces.

There are numerous objects on which it is advantageous to form close tolerance spherical surfaces. For example, such spherical surfaces are commonly employed on valves and valve seats, ball and socket joints, races for self aligning bearings and lenses for various optical instruments, to mention but a few.

Presently available lapping machines, while differing from each other slightly in construction, employ essentially the same functional elements and operate much in the same manner. In general, either the part to be lapped or the lapping tool is mounted eccentrically upon a spindle, gear or pulley such that the axis of the lapping tool interesects the axis of the part at an angle. During operation of the machine the axis of one of the above members circumscribes a conical surface, the angle between the respective axes remaining constant. This arrangement causes a wiping action, as well as relative rotation, to oc` cur between the two members.

The preferred form of the present invention, comprises a doubly eccentric arrangement of freely rotatable members operating in conjunction with a lapping tool for engaging the part to be lapped and a driving means for effecting relative rotation between the part, the lapping tool and the rotatable members.

An advantage of the subject lapping device, as contrasted with the above described lapping devices, is that it provides for a spiral motion between the part and the lapping tool, i.e., the angle between the axes of the part and the lapping tool changes constantly, varying from a maximum to a minimum, the latter corresponding to a position wherein the axes are coincident. This type motion results in a more perfectly spherical surface having an exteremely fine finish. Other advantages of this lapping tool are its simplicity of construction and operation.

It is, therefore, an object of the present invention to provide a device for lapping spherical surfaces.

Another object is to provide a device for lapping spherical surfaces which will effect a spiral motion between the part being lapped and the lapping tool.

Another object resides in the provision of a device for lapping spherical surfaces which is imple in construction and operation.

These and other objects and advantages will be apparent to those skilled in the art upon consideration of the following description of the appended drawings wherein:

FIGURE 1 is an elevation View, partly in section, of an embodiment of the invention as adapted for lapping the spherical surface of a valve;

FIGURE 2 is a series of diagrammatic representations, 2A, 2B, 2C, 2D, and 2E, of the motion of the centerlines of the lapping tool and valve shown in FIGURE 1;

FIGURE 3 is an elevation view, partly in section, of a device adapted for lapping two ball and socket joints simultaneously; and

FIGURE 4 is a cross-sectional View of the gear drive taken on the line 4 4 of FIG. 3.

Referring now to FIGURE l of the drawings, the lapping device of the present invention, generally indicated by the numeral 10, is shown as it may be mounted upon a supporting structure 11;, the latter including a lower horil Patented Feb. 2, 1965 lCe zontal portion i2, an integral upright portion if and an upper horizontal portion 14 which carries a rotatable spindle l having a pulley 17 afxed to its upper end. A V-belt l connects such pulley 17 with another pulley 19 which is attached to the shaft of an electric motor Ztl mounted on the upright portion 13 of the supporting structure. The part to be lapped, in this instance a valve 22 including a body portion 23 having a spherical surface 24 and an integral stem portion 2S, is attached to the spindle by means of a flexible, variable length member 26. It is desirable that member 26 be of variable length in order that it be capable of imposing a continuous downwardly directed force upon the valve Z2 as same bears against the lapping tool. As will presently become apparent, the variable length feature of member 26 arises out of a requirement to accommodate a variation in distance between the driving means and the valve as it bears against the lapping tool during the lapping operation. There are several devices which may be employed to attach the valve to the spindle. However, for the sake of simplicity, it has been found desirable to employ a section of fabric reinforced, rubber hose, such as ordinary welding hose which, by virtue of its resilience, offers the desired continuous downwardly directed force upon the valve. The internal diameter of the hose is slightly smaller than the diameters of the spindle and valve stem so that friction therebetween assures a common angular velocity.

To the lower horizontal portion l2 of the supporting structure there is aflixed, by means of bolts 28, a stationary member 29. A circular cavity 30 is formed in such member 29 wherein is disposed a bearing 31. Within the inner race of such bearing is positioned the journal 33 of a first, or lower, rotatable member 34. In order to assure free rotation of member 34, it is necessary to provide clearance between the lower surface of journal 33 and the bottom of cavity Si?, as well as between the under surface of the member 34 shoulder and the adjacent upper surface of stationary member 29. This may be accomplished most simply by making the diameter of the journal slightly larger than the inner diameter of the bearing inner race, so that the journal may be pressed or force fitted into the bearing to a level slightly above the latters lower surface.

A second, or upper rotatable member 35 is similarly mounted in a lower rotatable member 34 by means of bearing 3o disposed within cavity 38. The centerline 359 of the upper rotatable member 35 is offset from the centerline of lower rotatable member 34 so that an eccentric relationship is established therebetween. On the upper surface of rotatable member 35 is mounted a lapping tool all having a central bore 42 merging at its upper end in a flared concentric spherical surface 43 adapted to engage surface 24- of valve 22. Clamping devices 44 are employed to aix the lapping tool in position. The centerline 45 of the lapping tool bore is offset from the centerline 39 of the upper rotatable member 35, thereby introducing a second eccentric relationship into the lapping device.

In the form of the invention illustrated in FG. l the geometric relation between the members of the lapping device are as follows: the centerline 4t) of the lower rotatable member 34 is colinear with the centerline lo of spindle l5; and the centerline 45 of lapping tool il is offset from the centerline 39 of upper rotatable member 35 by a distance which is preferably equal to the distance separating the latter from the centerline ttl of the lower rotatable member 34, for a purpose to be explained below. With the centerlines 39, at), 4S, and 46 positioned in a common vertical plane, the condition of FlGURE 2A, the centerline 48 of valve 22 lies in the same plane and u is disposed at a maximum angle relative to the vertical, as in FIGURES 1 and 2A. As will be explained below,

during operation of the machine the valve Z2 and lapping valve by virtue of longitudinal compressive stresses within the hose induced as the valve bears against the lapping tool 41. Conventional lapping compound is employed between the valve and lapping tool and it is to be under-` stood that such pressure is not great enough to set up frictional forces between the valve and lapping tool sumcient to lock them together and prevent relative rotation therebetween. Thus rotation of the valve at a given rotational velocity, by actuation of electricmotor 20,"

results in a somewhat slower rotation of the lapping tool and upper rotatable member 35 because of the slippage permitted between the tool and valve. Rotation of member 35, in turn, causes a still slower rotation of lower rotatable member 34, as a result of frictional forces within bearing 36; As heretofore indicated, the paths of the centerlines 4S and 4S of lapping tool 41 and valve 22, respectively, are schematically illustrated in FIGURE `2. Since centerline e3 is normally angularly disposed with respect to the vertical, and not readily projectable in` a horizontal plane, for purposes` of illustration a point 50, corresponding to the point at which centerline 4S intersects the lower surface 51 of the valve, is used to show the path of such centerline.

Referring now to FIGURE 2A which corresponds to the positions of the respective centerlines shown in FIG- URE 1, during operation of the present lapping device the centerline 39 of the upper rotatable member revolves about centerline i0 of the lower rotatable member in a circular path indicated` at 52. The centerline 45 of `bore 42, in turn, also follows a circular path 53 about centerline 39. The point 5tl` is located in the same plane as centerlines 39, di?, 45, in the initial position shown in FIGURE 2A. It has been found that in general a satisfactory ratio between the rotational velocities of the upper rotatable member 35. and the lower `rotatable member 34 is approximately four-to-one. It is to be noted that the effectiveness of the present invention in accomplishing itsV intended purpose is not dependent upon such a relationship, and that the invention is not limited thereto since this ratio may vary over a relatively wide range.

Assuming a four-to-one ratio, `and countercloclzwise i rotation of the members, when the centerline 39 has rotated through 30 degrees about centerline 4b, the centerline i5V and point Sil have revolved 120 degrees about centerline 39. The resultant paths of centerline 45 and point are indicated at 55 and 56, respectively, in FIGURE 2B. It will be noted that the distance separating centerline 45 and point 50 in FIGURE 2B is lessthan their original separation as shown in FIGURE 2A. This results lfrom a decrease in the angle between the centerline of the valve and the vertical. of centerline 39, and 240 degrees rotation of centerline 45 and point Sil, the paths of the latter appear as in FIG- URE 2C. By making the distance between` the centerline t5 of the lapping tool 41 equal to the distance separating the latter from the centerline 40 of the lower rotatable After 60 degrees rotation member 34, at this` stage the centerline of the valve centerline 45 and point` 5@ has been reduced to zero. -f

Thus during a lapping operation, the relationship between` the valve and lapping tool varies between one of maximum eccentricity, as in FIGURE 2A, and one of Zero eccentricity, as in FIGURE 2C. The paths traversed by centerline 45 and point Sii in traveling from the positions shown in FIGURE 2A to that shown in FIGURE 2C are seen to be generally spiralinform. After passing through the positions of FIGURE 2C, the centerline 45 and point 5t) begin to separate and spiral outwardly as shown in FIGURE 2D. The complete paths of such centerline 45 and point ,56 areshown in FIGURE 2E, as indicated at 55 and 56,'respectively.

From the foregoing description of the respective paths of the valve and lapping tool, it may be readilyseen that, in addition to relative rotation between these two meni- `bers, there also occurs a wiping action,i.e., relative movement therebetween transverse to the axis of rotation of the lapping tool. Such wiping action prevents the formation of grooves on the valves spherical surface, thereby assuring the formation of a smoothly lapped surface.

Although the lapping device illustrated in FIGURE 1 has been described in conjunction with the lapping of a valve, it will be apparent to those skilled in the art that this device may also be employed to lap a valve seat, or to lap simultaneously both a valve and .a valve seat, Ithe latter arrangement being desirable in applications wherein an extremely close tolerance it between matching surfaces is required toeffect a virtually perfect seal at the valve-valveseat interface.

Referring now to FIGURE 3 there is shown another embodiment of the invention adapted for lapping simultaneously two ball and socket joints. This lapping device includes a supporting structure 61 which is preferably in the form of a box, one face of which is open, A main drive shaft 62 extends between the two opposite vertical sides 65, 66. One end of the drive shaft 62 extends beyond the side 65 of the supporting structure and has a main drive pulley` 67 afiixed thereto. Such pulley67 is connected, by means ofa V-.belt 63, with another pulley 69 on the shaft of -an electricmotor 'timounted on the top of the supporting `structure 61. On' the inside of the supporting structure there is atlixed to the main drive shaft pulleys 71, 72 and 73. The pulley 71 is connected by means of Vbelt174 witha pulley 7S aiiixed to a shaft 76, the latter being journaled within a bearing 77 in side 65 of the supporting structure 61. Pulley 72 is connected with a large pulley 79 by V-belt: 89, such large pulley `'I9 being rotatable about shaft 76 by virtue of a bearing 81 disposed therebetween. Near the edge of the large pulley 79 an aperture 32 is formed wherein is positioned a bearing 83.. Extending `through such bearing S3 is a shaft'85 to the inner end of which is attached a plate 86. To this plate'is affixed bymeans of clamping devices 39. one ofthe socket portions 87 of the assembled joint 38 to be lapped. To the opposite end of shaft $5 is attacheda pulley 91`whicl1 is connected, by means of V-belt` 92, to another pulley 93 whichis preferably integrallyconnected with pulley'75.

From the foregoing description of the vconstruction of the left hand members of the lapping device shown in FIGURE 3 it may be seen that actuation of the electric motor 70 results in the-rotation of the main drive shaft 62 and `pulleys 71, `72 which, `in turn, drive `integrated pulleys 75 and 93, and pulley 79, respectively. Rotation of pulley 93 lis transmitted through V-belt 92 to pulley 91,

thence to plate 86 and socket 87. Because ofthe relationship between the diameters of the respective pulleys,

the pulley 79 rotates at a relatively slow rate with respect to pulley 91. Thus while the joint 88 is being rotated in an orbit about the centerline. of shaft 76, the socket portion 87 thereof also rotates about the shaft S5, but at a considerably greater angular velocity.

The construction of the right hand portion ot the lapping device is essentially' the same as that of the left hand portion. Thus the components on1the right are designated by the same numerals as were used above to identify their counterparts on the left, the -subscript a being added to the right hand numerals to differentiate between the two sides.

In order to achieve a greater wiping action during the lapping operation, it is desirable that the pulleys of the right hand portion be rotated in a direction opposite to the rotation of those on the left. This may be effected by means of a small gear box 95, attached to the upper horizontal portion of the supporting structure 61, and enclosing a rst, or input, gear 96 having an input shaft 97 integrally connected thereto, and a second, or output, gear 96 having an output shaft 99 integrally connected thereto, the right hand end of the latter being rotatably supported in the right hand vertical member of supporting structure 61. The input shaft 97 is connected, by means of a pulley 101 and V-belt 102, to pulley 73 on main drive shaft 62, such that the input gear rotates in the same direction as the latter. The output gear and the output shaft 99, therefore, rotate in the opposite direction. Affixed to the output shaft 99 are pulleys 71a and 72a, the former being connected to pulley 75a by V-belt 74a, the latter being connected to large pulley 79a by V-belt 80a. Thus, as may be readily seen, pulleys 75a, 79a, 91a, 93a, as well as plate 86a and socket 87a, rotate in the opposite direction from their counterparts in the left hand portion. As will be apparent to those skilled in the art, the oppositely directed rotation between the right and left hand members of the lapping device is not a requisite condition for the satisfactory operation thereof. All that is required is relative rotation between such right and left hand members. For example,`by employing a pulley to drive large pulley 79a whose diameter is somewhat larger than pulley 72, relative rotation between large pulleys '79, 79a would be effected and, consequently, lapping of the joints would occur.

After mounting the assembled socket portions 87, 87a of the ball and socket joints 88, Sa upon the mounting plates 86, 86a, respectively, the ball portions 105, 105a of the joints are connected with lan expansible member 106 which includes a pair of stem members 107, 107a, the outer ends of which are threadably engaged with balls 105, 105er, respectively. The inner ends of such stem members are enlarged, as indicated at 108, 108m and are retained within a tube 109 comprising a pair of sleeve members 110, 110a aligned end to end and threadadly connected by means of an intermediate collar member 111. To the outer ends of members 110, ln are connected apertured cap members 112, 112m A spring 113 is disposed within the tube 109 between ends 108, 108:1 of stem members 107, 107a which serves to bias the latter outwardly, thereby causing a continuous bearing force between the ball portions 105, 105%: and the socket portions 87, 87a of the joints 38, 86a. Conventional lapping compound is employed intermediate these ball and socket portions. The internal diameter of tube 109 is slightly larger than that of stem enlargements 108, 108:1 such that the latter are freely slidable therein. This interconnection between the ball portions of the joints, in conjunction with the eccentric mounting of the joints upon pulleys 79, 79a, provides the desired doubly eccentric relationship between the rotatable members of the lapping device.

Since the large pulleys '79, 79a are rotated in opposite directions during operation of the lapping devices, the linear separation between the ball and socket joints varies constantly between a maximum separation and a minimum separation, the former corresponding to the positions shown by full lines, and the latter corresponding to the positions shown by the broken lines .at 114 and 114g. This variation in separation between the joints is made possible by the slidable relation between the stems 107, 107a and the tube 109. Such maximum and minimum linear separations correspond respectively to maximum and minimum angular separations between the axis of the ball and the axis of the socket. As will be apparent, with the pulleys 79, '79a rotating in opposite directions, preferably at the same speed, the total angle through which the balls move relative to the sockets is equal to twice the maximum angular separation therebetween.

Although the ball portions of the joint are free to rotate with respect to tube 100, they are prevented from rotating at the same rate as the socket portions by the wiping action resulting from the constant angular variation therebetween resulting from the wobble action of the tube. Thus, during operation of this lapping device, there occurs both a relative rotation and a wiping action between the ball and socket portions of the joints. The combination of these two types of motion results in surfaces which are virtually perfectly spherical and have an extremely tine finish.

While it 4is not required for the satisfactory operation of the lapping device shown in FIGURE 3, it is desirable that the shafts 76, 7nd, about which the large pulleys 79, 79a rotate, be axially aligned, and that the shafts 85, 85a, about which the socket portions S7, 87:1 of the joints 88, 88a rotate, be spaced from the shafts '76, 76a, respectively, by equal distances. Such alignment and spacing results in the centerlines of the sockets 87, 87a and the centerlines of the balls 10551 coinciding when same are in positions 114, 114m. By so reducing the minimum angle between such centerlines to zero, greater wiping angle is achieved between the ball and socket portions of .the joints 88.

Although only certain preferred embodiments of the invention have been herein shown and described, it is not to be construed that the invention is limited thereto, as numerous modifications will be apparent to those skilled in the art, and the invention is to be given the broadest possible interpretation within the terms of the following claims.

What I claim is:

1. In a device for lapping simultaneously two ball and socket joints each comprised of a ball and a socket portion, the combination of a supporting structure having opposite wall portions, a pair of relatively large rotatable members mounted on said wall portions facing each other, mounting means carried by each of said members for rotation about axes displaced from the axes of rotation of said rotatable members for mounting each of the ball and socket joints thereon to permit relative rotation between their respective ball and socket portions, variable length means interconnecting the ball portions of the joints while biasing said portions against the socket portions and 4imparting a wobble action to said ball portions, and driving means for effecting said relative rotation between said ball and socket portions and for effecting the said wobble action of said interconnecting means by driving said large rotatable members in rotation relative to each other.

2. In a device for lapping simultaneously two ball and socket joints each comprised of a ball and a socket portion, the combination of a supporting structure having opposite wall portions, a relatively large rotatable member mounted on each of said wall portions, a rotatable mounting means eccentrically positioned on each of said large rotatable members for mounting the ball and socket joints, variable length means interconnecting said ball and socket joints, a first drive shaft for driving one of said large rotatable members in one direction, a second drive shaft for rotating the other said large rotatable member in the opposite direction, means associated with each of said mounting means for rotating said mounting means and the socket portions of said joints relative to said large rotatable means.

3. A device for lapping ball and socket joints comprising, in combination, a support structure including a pair of spaced apart support members, a rotatable member mounted upon each of said `support members, rotatable g l mounting means eccentrically carried upon each of said rotatable members and at least one of which includes provision for mounting a ball and socket joint comprised or" ball and socket portions to permit relative swivel movement between the said ball and socket portions, variable length means linterconnecting said rotatable mounting means being connected through said ball and socket joint to one of said rotatable mounting means and at its other end also permitted swivel movement, said variable length means including means maintaining the said ball and socket joint portions in abutment, and driving means for eecting said relative swivel movement between said joint portions by driving said rotatable members in rotation relative to each other and said rotatable mounting means in rotation relative to said rotatable members.

4. A device for simultaneously lapping two ball and each including provisions for motmting ball and socket joints comprised of ball and socket portions to permit relative swivel movement between'tlae said ball and socket portions, variable `length means operably interconnecting said rotatable mountingv means through said ball and socket joints and provided'with means for biasing the said ball and socket joint portions into abutment for lapping coaction, and driving means for effecting said relative swivelmovement between said joint portions by driving said rotatable .members in rotation relative tol each other and said rotatable mounting means in rotation relative to said rotatable members.

References Cited by the Examiner UNITED STATES PATENTS 3/34 Capps 5l-27 7/ 60 Goulet et al 51--27 JOHN C. CHRISTIE, I. SPENCER OVERHGLSER,

Examiners. 

4. A DEVICE FOR SIMULTANEOUSLY LAPPING TWO BALL AND SOCKET JOINTS COMPRISING, IN COMBINATION, A SUPPORT STRUCTURE INCLUDING A PAIR OF SPACED APART SUPPORT MEMBERS, ROTATABLE MEMBERS MOUNTED UPON SAID SUPPORT MEMBERS, MOUNTING MEANS CARRIED BY EACH OF SAID ROTATABLE MEMBERS FOR ROTATION ABOUT AXES DISPLACED FROM THE AXES OF ROTATION OF SAID ROTATABLE MEMBERS, SAID MOUNTING MEANS EACH INCLUDING PROVISIONS FOR MOUNTING BALL AND SOCKET JOINTS COMPRISED OF BALL AND SOCKET PORTIONS TO PERMIT RELATIVE SWIVEL MOVEMENT BETWEEN THE SAID BALL AND SOCKET PORTIONS, VARIABLE LENGTH MEANS OPERABLY INTERCONNECTING SAID ROTATABLE MOUNTING MEANS THROUGH SAID BALL AND SOCKET JOINTS AND PROVIDED WITH MEANS FOR BIASING THE SAID BALL AND SOCKET JOINT PORTIONS INTO ABUTMENT FOR LAPPING COACTION, AND DRIVING MEANS FOR EFFECTING SAID RELATIVE SWIVEL MOVEMENT BETWEEN SAID JOINT PORTIONS BY DRIVING SAID ROTATABLE MEMBERS IN ROTATION RELATIVE TO EACH OTHER AND SAID ROTATABLE MOUNTING MEANS IN ROTATION RELATIVE TO SAID ROTATABLE MEMBERS. 